Various methods have already been proposed for analyzing a structure of a tune. Specifically, by analyzing a waveform of a tune as illustrated in the upper part of FIG. 1, it is found that the tune has a structure as illustrated in the lower part of FIG. 1. That is, assuming that time progresses from the left of the figure to the right, the tune starts with “Introduction” and the subsequent parts thereof are composed of, in order, “Chorus”, “Interlude”, “Verse A”, “Verse B”, “Chorus”, “Chorus”, “Interlude”, and so on. Then, based on the result of such analysis, sections corresponding to chouruses are identified in the tune, for example.
Hereinafter, a part of a tune that is positioned in the middle of the time and involves a change in motif and which, in particular, is the roost alluring part of the tune will be referred to as a “chorus”, In addition, a unit for making a meter will be hereinafter referred to as a “beat”. That is, heats can be counted as they each have a constant temporal duration, and positions of the beats in a measure produce variations in accent (i.e., downbeats and upbeats), and different combinations thereof result in different, meters.
There is also a method in which features are extracted from input audio data; the degree of similarity between the features is calculated to list repetitive sections; the listed repetitive sections are integrated; the detection of repetitive sections involving a modulation is performed; the repetitive sections involving a modulation are integrated; and a section that is appropriate as a chourusesection is selected from the integrated repetitive sections (see, for example, Patent Document 1).    Patent Document 1: Japanese Patent Laid-Open No. 2004-233965